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fbdev: Hot-unplug firmware fb devices on forced removal

Hot-unplug all firmware-framebuffer devices as part of removing them via remove_conflicting_framebuffers() et al. Releases all memory regions to be acquired by native drivers. Firmware, such as EFI, install a framebuffer while posting the computer. After removing the firmware-framebuffer device from fbdev, a native driver takes over the hardware and the firmware framebuffer becomes invalid. Firmware-framebuffer drivers, specifically simplefb, don't release their device from Linux' device hierarchy. It still owns the firmware framebuffer and blocks the native drivers from loading. This has been observed in the vmwgfx driver. [1] Initiating a device removal (i.e., hot unplug) as part of remove_conflicting_framebuffers() removes the underlying device and returns the memory range to the system. [1] https://lore.kernel.org/dri-devel/20220117180359.18114-1-zack@kde.org/ v2: * rename variable 'dev' to 'device' (Javier)

Thomas Zimmermann committed 4 years ago

Commit 27599aa1 parent 31b04882 files · +27 −3Browse files

Showing the changes to include (1 of 2 files). Show all

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include/linux/fb.h+1−0
@@ -502,6 +502,7 @@ struct fb_info { · 501 unmodified lines
502502 } *apertures;
503503
504504 bool skip_vt_switch; /* no VT switch on suspend/resume required */
505+ bool forced_out; /* set when being removed by another driver */
505506 };
506507
507508 static inline struct apertures_struct *alloc_apertures(unsigned int max_num) {

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